The American Bible Society estimates there are about 900 English translations and paraphrases, but only a few are widely accepted by the church. For the sake of brevity, I’m just going to address reasons for New Testament translations:
Families of texts
Some definitions first. A “Manuscript” is an ancient handwritten copy of the Bible, and a “Text” is someone’s compilation of a set of manuscripts attempting to give a good representation of the originals. English translations are made from mostly two texts:
The Majority Text is translated from the majority of Greek manuscripts, and we have about 8,000.
The Westcott-Hort text-type (WH) is based on a few manuscripts, but these are older than those of the Majority Text. The dilemma is, “Should we depend on the oldest but the few or the newer but the larger library of manuscripts?”
As a result, we have two “families of Bibles” produced. The King James Version (KJV) and New King James Version (NKJV) are translated from the Majority Text. Almost all other modern translations are translated from the Westcort-Hort text. All are well accepted since there is really no doctrinal difference.
To see some of the differences, look at Mark 16:9-20. The oldest manuscripts don’t have this passage included. So, there is usually a translation note telling you so in the center column or elsewhere.
Philosophy
There are different philosophies of translations, too. There are the “word-for-word” translations where each Greek word in the text is directly translated then those words are formed into phrases in English. Examples of word-for-word translations would be the KJV, New American Standard Bible (NASB) and the English Standard Version (ESV). Two benefits of word-for-word translations is we are less likely go see the translator’s bias in the translation, and it helps in Bible study to know exactly what is being said.
Then there are idiomatic translations. These translate meaning as well as actual language. In Spanish, “You are pulling my hair” is similar to the English, “You are pulling my leg.” Idiomatic translations such as the New Living Translation and New International Version would translate it “You are pulling my leg,” while the NASB would translate it exactly as stated. The benefits here are a smother read and a clearer meaning to the reader.
Both of these types of translations are occasionally revised and improved when new understanding of the language or better understanding of a particular portion of the text occur.
And, there are paraphrases like the old Living Bible and the Philips Paraphrase. These are not translations at all but just paraphrases of what the author thought the biblical text was saying.
Lastly, there are biased “translations” like the Watchtower’s New World Translation (NWT) which is not a translation at all but is presented as such to the readers. The Watchtower has changed portions of the Bible to support their own doctrines and convince the reader the Watchtower is correct in its teaching.
Commercial
Some translations do have commercial value, of course. A scholar or group of scholars may produce a translation which is attractive to a publishing company. The translation can be licensed to that publisher to be used in it’s Bible study helps and to be published as a translation, study Bible, etc. Under the license, the publisher can also use the translation may be used in their daily devotionals, collections of verses for a particular like “Verses for the small businessman.”
This can be done without copyright problems. Also, if the translation is a particularly popular one, the customer must come to that publisher to purchase that translation.
Recommended Book: An Introduction to the Bible by Geisler and Nix. You can find this book on the Recommended Books link under the main menu at the right side of bottom of the age.
Believers Armed and Dangerous 